Cerith Snails, Cerithium sp.

2 introduced on the 10th November 2016. Another 2 added 13th May 2017 but one doesn't appear to have moved since so the total may already be down to 3. :o(

Update 30th Oct 2017: The Clibanarius antillensis hermit (was found to be wearing a new Cerith shell this morning, I think he must have killed to acquire his new home as the snail appeared to be alive and well the day before. I do have lots of spare shells but clearly they are not acceptable.